A scanning apparatus such as a sheet-feeding type scanning apparatus or a flatbed scanning apparatus is one of the widely-used office machines for scanning a paper document and converting the paper document into an electronic document. Generally, the conventional sheet-feeding type scanning apparatus comprises a feeding mechanism, a scanning module, and a calibration plate. The feeding mechanism is used for feeding a paper into a conveying channel. The scanning module is fixed at a downstream position of the feeding mechanism and located at a side of the conveying channel for capturing an image of the paper document. The calibration plate is located at another side of the conveying channel and faces the scanning module. The calibration plate provides a white background basis for calibrating the scanning module in order to avoid brightness distortion of the scanned imaged. Moreover, for allowing the paper to be smoothly transported across the scanning module, the calibration plate is fixed on the office machine to provide a function of pressing the paper. Consequently, the quality of the document image will not be impaired.
However, if the conventional sheet-feeding type scanning apparatus is used for scanning a small-sized document such as a name card, some problems may occur. For example, since the white background of the calibration plate uncovered by the document is still scanned as a portion of the scanned image, the size of the scanned image is increased. Under this circumstance, the capacity of the storage medium is wasted. For shortening the size of the scanned image, the conventional sheet-feeding type scanning apparatus or the computer which is in communication with the conventional sheet-feeding type scanning apparatus may utilize a conventional image processing program to allow the document image and the background image of the scanned image to be separated from each other. Consequently, only the document image of the scanned image is retained. However, since most of the widely-used documents are white and the calibration plate is also white, it is difficult to recognize the border between the document image and the background image of the scanned image. Under this circumstance, the task of removing the background image from the scanned image becomes more difficult.
Moreover, as previously described, the scanning module and the calibration plate of the conventional sheet-feeding type scanning apparatus fail to be moved relative each other. If some specks appear on the calibration plate, the scanning module can only acquire abnormal image data. Since the scanning module is unable to acquire more image data of the calibration plate by moving the scanning module or the calibration plate, the scanning module fails to recognize whether the image data are abnormal. Under this circumstance, the scanning module will perform a brightness calibration according to the abnormal image data. Consequently, the efficacy of the brightness calibration is usually unsatisfied.
Therefore, there is a need of providing an improved scanning module in order to overcome the above drawbacks.